The present invention relates to a method and an apparatus for regulating and controlling the current between amodes and cathodes in an electrolysis cell having adjustable, variable, anodes. The use with cells for the electrolysis of alkali metal chlorides with mercury cathodes will be particularly described below, although the apparatus and the process may also be used with many other kinds of electrolysis cells.
The graphite anodes which so far heretofore were usually employed in electrolysis of alkali metal chlorides are subjected during electrolysis operation to a constant burning off, with the space between the anodes and the cathode as a result becoming continually larger, and when the burn-off of the individual anodes is varying a varying anode current intensity in the individual anodes will be the result. It therefore is necessary in order to maintain economy of the electrolysis operation and to maintain a uniform current intensity in all anodes to subsequently adjust the anodes at certain time intervals.
On the other hand, coated, activated titanium anodes are being ever more frequently employed in the electrolysis of alkali metal chlorides since they for quite some time maintain their configuration for the entire duration of the electrolysis process. In order to maintain with respect to the economy of the electrolysis process the cell voltage as low as possible, the spacing between the anodes -- for graphite anodes as well as also for titanium anodes -- and the cathode is to be maintained as small as possible, however, and thus short-circuits between anodes and cathode and a non-uniform current load of the individual anodes, for example caused by deposition of amalgam butter and the change in height of the cathode resulting therefrom, can no longer be precluded. This may result in damage to the anodes and, moreover, to parts of the electrolysis cell. Furthermore, with coated titanium anodes overloads for prolonged periods of time that exceed the nominal load eventually lead to damage of the active layer and, thus, to a reduced service of life of the active layer.
Apparatuses for regulating the spacing or distance between the anodes and the cathode of an electrolysis cell and, thus, also for regulating the anode current are known, in which the magnetic field produced by the anode current is utilized for controlling the apparatus, with protective gas tube contacts or solenoid-operated switches being used as sensors. Besides the magnetic field produced by the anode current, a further magnetic field must still additionally be artificially produced and the signal for controlling the apparatus is obtained from the sum or the difference of these two magnetic fields. The generation of the second, artificial, induced magnetic field that is required with these known apparatuses involves a considerable drawback, since for generation and adjustment thereof additional loads, coils and control elements are required. A further drawback is that the protective gas tube contacts and solenoid-operated switches constitute mechanically operating structural elements and are subjected to all disadvantages and interferences inherent to electrical structural elements having mechanically operating contacts.